1. Field of the Invention
The present invention relates to a perpendicular magnetic recording head including at least an inductive magnetic transducer for recording, and a magnetic recording apparatus including a perpendicular magnetic recording head.
2. Description of the Related Art
In recent years, an improvement in performance of a thin film magnetic head which is included in a magnetic recording apparatus such as a hard disk drive has been sought in accordance with an increase in the areal density of a magnetic recording medium (hereinafter simply referred to as “recording medium”) such as a hard disk. As recording systems of the thin film magnetic head, for example, a longitudinal recording system in which a signal magnetic field is oriented in an in-plane direction (a longitudinal direction) of a recoding medium and a perpendicular recording system in which a signal magnetic field is oriented in a direction orthogonal to a surface of the recording medium are well known. At present, the longitudinal recording system is widely used, but in consideration of market forces in accordance with an improvement in areal density, it is assumed that the perpendicular recording system instead of the longitudinal recording system holds promise for the future, because the perpendicular recording system can obtain advantages that higher linear recording density can be achieved and that a recording medium on which information is recorded is not easily affected by thermal decay.
The perpendicular recording system thin film magnetic head (hereinafter simply referred to as “perpendicular magnetic recording head) includes, for example, a thin film coil generating a magnetic flux for recording, and a pole layer extending from an air bearing surface to the rear and guiding the magnetic flux to a recording medium so that the recording medium is magnetized in a direction orthogonal to a surface of the recording medium. In the perpendicular magnetic recording head, when a magnetic flux for recording is generated through passing a current through a thin film coil, the magnetic flux is emitted from the front end of the pole layer to generate a magnetic field for recording (a perpendicular magnetic field), so the surface of the recording medium is magnetized by the perpendicular magnetic field. Thereby, information is magnetically recorded on the recording medium.
Improvements in the performance of the thin film magnetic head are in increasing demand. In consideration of such a technical background, recently as means of improving the performance of the thin film magnetic head, for example, in addition to changing the recording system from a longitudinal recording system to a perpendicular recording system, an attempt to form the magnetic domain structure of the pole layer which performs a recording process appropriate. More specifically, for example, a thin film magnetic head including a pole layer which has a closure domain structure having a magnetic domain narrowed from the back end to the front end in order to secure better recording performance through smoothly transferring a magnetic flux is known (for example, refer to Japanese Unexamined Patent Application Publication No. H11-328615).
In order to secure the operating characteristics of the perpendicular magnetic recording head, for example, in order to prevent information erasing without intention at the time of non-recording, it is necessary to make the magnetic domain structure of the pole layer appropriate. The “information erasing without intention at the time of non-recording” means a failure that at the time of non-recording, that is, in a state where a thin film coil is not energized (a state where a magnetic flux for recording is not generated), information recorded on a recording medium is erased without intention because a magnetic flux remaining in the pole layer (residual magnetization) is leaked from an air bearing surface due to the magnetic domain structure of the pole layer as a portion where the magnetic flux for recording is emitted. However, in a related art, as described above, it is known that the magnetic domain structure of the pole layer has an influence on the smooth transfer of a magnetic flux, but sufficient knowledge about a causal relationship between the mechanism of information erasing without intention at the time of non-recording and the magnetic domain structure of the pole layer is not obtained, so how to set the magnetic domain structure of the pole layer for preventing information erasing without intention at the time of non-recording is an issue. Therefore, in order to secure the operating characteristics of the perpendicular magnetic recording head, the establishment of a technique to be able to prevent information erasing without intention at the time of non-recording through making the magnetic domain structure of the pole layer appropriate is desired.